Attapulgite used in the catalyst is a fibrous clay. The chemical analysis of attapulgite clay shows the presence of oxides such as SiO.sub.2, Al.sub.2 O.sub.3, MgO, Na.sub.2 O, Fe.sub.2 O.sub.3 and water along with traces of nickel, chromium, zinc, copper, lead, tin, vanadium and silver and the composition of Attalpulgite in form of mole percent is as follows:
SiO.sub.2 - - - 55.03% PA1 Al.sub.2 O.sub.3 - - - 10.24% PA1 Fe.sub.2 O.sub.3 - - - 03.53% PA1 MgO - - - 10.49% PA1 K.sub.2 O - - - 00.47% PA1 H.sub.2 O.sup.- - - - 09.73% PA1 H.sub.2 O.sub.+ - - - 10.13%
We have carried out extensive research in respect of the use of attapulgite for catalyzing chemical reactions. Some of the other uses of attapulgite are listed here:
It is used as a polymerization catalyst, in refining vegatable oils and fats, as a carrier for granular and powdered agricultural chemicals (insecticides and herbicides), in petroleum refining, decolourising, neutralising, brightening and for desulphurization.
It is also used as an oil base and water base foundry sand binders, latex paint thickener, gelling agent, polishing-suspending agent for abrasives and as a wax emulsion stabilizer.
We have observed during our research that attapulgite can be used as catalyst for alkylation reaction. In our continued work developing attapulgite as a catalyst for selective alkylation of aromatic amines we have observed that when attapulgite is impregnated with a combination of iron oxide and oxides selected from transition metals of the periodic table, the effect of alkylation is greatly enhanced. The catalyzing activity of the resultant catalyst for the alkylation reaction, in particular for ortho and N-alkylation is found to be enchanced.
Alkylated aromatic amines are useful in a broad range of applications. Particularly ortho-alkylated aromatic amines are used as intermediates for producing dyes, Insecticides, resin stabilizers, rubber compounding ingredients and the like.
In the Japanese patent publication No. 47-24014/72 a method has been described in which aromatic amines such as aniline and the like are reacted with alkyl aluminium halide, followed by reaction of the resultant mixture with olefins. In Japanese patent No. 50-137934/75 a method has been described in which aromatic amines are reacted with lower olefins in the presence of a catalyst consisting of aluminium anilide and halogenated hydrocarbons. The above mentioned processes have advantages that the reaction activity and selectivity are high, but due to the involvement of very high temperatures and pressures there is a disadvantage that the reaction apparatus suitable for the conditions has to be used, and since a substantial amount of the catalyst is used, post treatment for removing the catalyst from the reaction mixture is troublesome.
Other prior art processes for producing ortho alkylated aromatic amines include methods like that proposed in U.S. Pat. No. 2,814,646 in which an aromatic amine is reacted with olefins under heating in the presence of an aluminium anilide catalyst. The disadvantage of this process is that the reaction activity is low, although the selectivity in the product is high. In U.S. Pat. No. 4,351,958 a process for producing ortho-alkylated aromatic amines in which, an aromatic amine is reacted with olefins, has been described at a temperature in the range of 200-500.degree. C. with reaction pressure from 1-30 kg/cm.sup.2 and a catalyst comprising iron oxide as a main constituent. A variety of catalysts have been tried by this method and the maximum selectivity of 2,6-dialkylaniline is reported as 51.6% under optimum conditions.
N-Alkylated aromatic amines are useful in a broad range of applications. They are used as raw materials for synthesis of organic chemicals, and as intermediates for producing dyes, in agrochemical industries like fertilizers, as resin stabilizers, rubber compounding ingredients and the like.
The vapor phase catalytic reaction of aniline and ethanol is the method of choice for the industrial production of N- ethylaniline. In European patent EP 39,061 a method has been described wherein aromatic amines are prepared treating olefins with ammonia and a primary or a secondary amine in presence of Ruthenium or ferric compound dissolved in liquid phase solvent. The temperatures and pressures employed being 100-250.degree. C. and 1-12000 psig.
In Japanese patent 58,146,534 a method has been described in which N-alkylated anilines are prepared by alkylation of H.sub.2 NC.sub.6 H.sub.5-n X.sub.n with alcohols/ethers in gas phase in presence of S ion, Ti and Zr catalysts.
Other prior arts for producing N-ethylaniline include both liquid phase methods and vapor phase methods. These processes differ mostly in the type of catalyst used. The liquid phase processes produce N-ethylaniline with equal quantities of the diethylated products, and are still in vogue.
Several combinations of the catalyst have been reported, in particular alumina promoled with different metal oxides appears to have been widely employed. Zeolites have been used extensively as catalysts for the production of N-alkylated anilines. Bauxite is also proved to be a good catalyst for this reaction.
The main object of the present invention is to provide an improved process for the preparation of alkylated aromatic amines.
Another object of the present invention is to provide an improved process for the preparation of ortho-alkylated and N-alkylated aromatic amines. Yet another object of the present invention is to provide an improved process for the preparation of ortho-ethyl or ortho-methyl or N-ethyl or N-methyl amines. The invention is based on the findings that when attapulgite is impregnated with a combination of iron oxide and oxides selected from the transition metals of the periodic table, the activity of the resultant catalyst is enhanced for selective alkylation of the aromatic amines.